Gastight storage battery and method of manufacturing same



. April 21, 1953 G- NEUMANN 2,636,058

GASTIGHT STOR1'\GE` BATTERY AND METHOD OF-, MANUFACTURING SAME Georg NEUMANN 0,'2 0,'@016 als l' 1,'2714' A v 'ENT April 21, 1'953 @.NEUMANN 2,636,058

GASTIGHT STORAGE BATTERY AND METHOD OF MANUFACTURING SAME Filed NOV. 18, 1950 2 SHEETS-SHEET 2 mln/ral? Georg NEUMANN ay 27H5 5' MW@ Patented Apr. 21, 1953 GASTIGHT STORAGE BATTERY AND METHOD OF MANUFACTURING SAME Georg Neumann, Paris, France, assigner to Buy reau Technique Gautrat, S. A. R. L., Les Lilas,

France, va society of France g i Application November 18, 1950, Serial No. 196,376 i In France November 22, 1949 Thefpresent invention relates to storagetbatteries which are gastight even under pressure, and inv particular to alkaline storage batteries made according to the U. S. patent application of Georg Neumann and Uscha Gottesmann, Ser. No. '73,608,1iled January 29, 1949, now Patent Number 2,571,927, October 19, 1951, for. ,Electrolytic Cells, and in Particular Alkaline Cells, of which this, application is a continuation-impart, and to methods of manufacturing such batteries.

i It is known to include, in the positive electrode of a gastight alkaline storage battery, nickel oxideswhich constitute the positive active material. With these nickel oxides is incorporated at least one body ensuring conductivity, for instance graphite. l y Y It isalso known to include, in the negative electrode of such a storage battery, cadmium or iron or a mixture oralloy of these metals, which may be in the form of oxides or hydrates.

l. It should be noted that` both the positive and the negative electrodes may be constituted by a plurality of plates. l 1

vIn these gastight storage batteries, dangerous internal 4pressures are avoided by causing the gases evolved during charging or at the end of this operation to recombine with the active material of the electrodes v (see. the above mentioned prior application). i

When, in a battery including a plurality of storage cells connected in series, discharge is allowed' to gc on until one of the cells, of an amp-hr. capacity slightly lower than that of the other cells, becomes inverted (slight diierences in amp-hr. capacity are unavoidable even if the rated capacities of the respective cells are equal) and current is still caused to flow in the same direction, there are produced on the negative electrode of this cell oxides which are difficult to reduce and which impair the subsequent qualities of the storage battery.

i In additionpto this detrimental consequence of whatv will be hereinafter called an overdis.

charge, there is, in thecase of a gastight storage battery, another drawback due to the fact 1o claims. (c1. 13e-7) i that, in such .a storage battery, means are provided for enabling the gases evolved in the cellto .recombine but that these means were provided, up

to now, concerning -the gases evolved near the end of charging and do not apply to the gases .overdischarge might` be particularly detrimental 450 evolved during overdischarge. It follows that an' in the case of a gastight` storagebattery due to s I the increaseofinternal pressuretherein.l 1

riesaminare iherisksraumg from overdischarge in the case of slight unequalities in the` amp-hr. capacities of gastight cells connected in series are obviated by giving the negative electrode of each cell a capacity higher than that of its positive electrode and by closing the gastight vessel of each of these cells, when they are being manufactured, only when the two electrodes thereof have been brought to such a state of oxidizing or charging that the negative electrode is charged to a higher degree than the positive electrode, the difference of-charge between the two electrodes being however at most equal to the difference between their capacities.

In other words, according to my invention, when the positive electrode of a gastight storage cell is fully oxidized, andtherefore fully charged, the amount of oxidizable metal then present on the negative electrode corresponds, for this electrode, to a possibility of discharge higher than that of the positive electrode.

Preferred embodiments of my invention will b e hereinafter described with reference to the accompanying drawings, given merely by Way of example, and in which:

Figs. 1 to 4 show the discharge curves of gastight storage cells, the voltages indicated by the curves of Figs. 1 to 3 being measured with reference .to a zinc electrode immersed in the solution of the same discharge cell;

Figs y5 and 6 are respectively a longitudinal section and a cross section of a storage cell made' according to my invention.

Fig. 1 shows the discharge curves of an alkaline storage battery of a known type, the positive electrode of this accumulator including graphite mixed with nickel'oxide. The discharge curve I of such a cell practically stops near point D. However discharge further takes place along portion AB ofthe curve, probably owing to the presence of oxygen included in the above mentioned graphite.

:The discharge curve of a negative ironcadmium electrode is shown by curve 2 when this electrode is given a usefulcapacity substantially equal to the useful capacity of the positive electrode. In this case, the potential of this negative electrode remains at the same value along portionA EF oi the curve. Then it rises suddenly.

At point G, where curves l and 2 cross each other,

the polarity of the storage battery is reversed.A

which drops to zero for the abscissa of point G,

"toubecome negativeA for higher abscissaav The curves of Figs. 2 and 3 relate to storage cells made according to my invention.

In the case of Fig. 1, the negative electrode is made only of the usual metals. Owing to my invention, useful discharge of the negative electrede is prolonged as far as a point F (curve 2 of Fig. 2*)*the abscissa of which is greaterl than that of point F of Fig. 1. Thus, while the storage cell is practically discharged for the abscissa of points D and D', the negative electrode cany still be oxidized between points D and F under Vthe effect of the current delivered by other cells in series with that considered'. Consequently,.th`e risks of injur,7 caused by overdischarge of this gastight cell are considerably reduced.

However, it must be well understood tlfrat` this is not due only t the fact that the capacity of the negative electrode is higher than thatv oi the positive electrode, but also` to the fact that, When the gastight vessel of the cell was closed, during the manufacture thereof, the useful charge` of thenegative electrode had `been brought toa higher ypoint than the useful charge of the positive electrode, these Itwo electrodes being then capable, due to the characteristics of sealed dis. charged cells, of receivingTA only substantially equal' charges which couldy hardly make itpossible to over-'charge one of them after the other is fully charged, whereas vthisf-can easily take plaeein the case of anopen c ell.

l. will noWgive a numerical example,y based upon the curve of Fig, 4; to illustrate this fea.'- ture.

ANAIf'itv is supposed that the useful capacity of the positive electrode is l amp.hr., thefnegative electrode will be given, according to common practice,` a capacity higher than 1 amp-hn Andi the vessel; ofy the gastight cell; willl be sealed when the charge received by the,v negative electrode and, Capable. Qf beine delivered by it is higher theme@ charge received-by the. positive eletde,

and VCapable of berledelivrediby it The difierence between these'chargesinay depend upon Various circumstances, but it Shrud always: be chosen. higher than, the wlerancesy of, capacity of the' 'o 'tive elettrodeswhen they are, manufactured! ii a derence of, (L amp--hr- '1e to exist' between they 'charges ofthe two. electredes. the capacityei the., negative electrode is t9, be. at least eguali@ 1.2.5; empf-hr.- andthe. iollowing conditions are to be complied with:

A li the vessel, Qf the4 tank is Sealed` when the nickel Qi the we itlveeletrode can. deliver no. C theneeative electrode must have been pre ously charged so'. as to be, able to. deliver..

042,5 'ama-hrs.

jtlel vessel is1 sealed, when' the nickel' QI; the metil/e electrode, is capable. of delivering. the, ChalefleSFfQndIlg "0.0 its maximum Capa'y. of'lampshr., thenegative electrode mustyhave been previously charged so as tov be able to de.. liver 11,25. ame-ht; f'

gina' general way,if the positive electrode 'has been chargedsoas to be able to deliver'a'jvalue ranging frein-dto 1- amp-hr. markecl'in ordinatesl on the curve of Fig.` 4, thenat-the timeofclosing of the vessel,- thev negative electrode must have been ehargedto a value corresponding to,y the abscissaofl the correspondingvjpoint ofthis CURVE.

.Eiowewer, .itV is advantageous,` in the casethatV isbeing considered, togive the negative electrode a.-.capacitystilli higher.y than 1.25 amp-hr., for instance a capacity yof L5 ampi-hr., 'while-leaving the difference. between. the chargesfofthe tWof plated steel;

electrodes equal to 0.25. Thus, the negative electrode will never be so charged as to be able to deliver more than 1.25 amp-hr. and there will remain on this electrode, after full charging of the cell, an uncharged portion corresponding to 0,25, amp-hr. I'This unehargedpportionw-ill play, near the endof the charging of the cell. the useful part indicated in the above mentioned 4prior patent application, which consists in delil,

.the time whenfhydrogen starts being evolved at laying, inA the course of the charging operation,

the negative electrode.

In Figs.v l 11023,` this last case is illustrated-by 'the ldotted lines ordinates and abscissas.

If, now, viii-order 'to prolong the possibilities'of 'discharged-'lille negative electrode, I make use v used, .it seems particularly advisable,v inv 'the-case of an alkalinelstorage cell..totmake-useofooppen for instanceirr the` powdery-.former `Airl-Jam'algarn with` mercury, ormerelywlxed orr ther-metallicI envelope-of the bags oontainingfthe electrodeg-or again-'in the! form` ofj separate plates-a Owing, lto the4 use-oi an auxiliary metal: com

plying with these conditions, after; discharge or;

the ymain metal or metals of the negativefelectrode of. a. weak celloff thel battery,

thereof itiligl'-)f willfinclud'ey a-portionI-IJ;V at-.a level higherthan that of Consequently, the`v terp` have;A already passed theend` of. their VusefilljfV Furthermore, and this-is,y stillmore` discharge. I important', anyvl amountsof oxygerras vmighttend, tof` appearon the negative. electrode; will combine withsad auxilia-rymetal andfoxidize it.v- "Pherisks above pointed outwillfthusfbe consi,derablyl reduced;

Furthermore-, thefaot; that* the ovewoltagbe,of-`

thek auxiliaryv metal-g with respect tov 'hydrogenisr higher than that of the `lmainmetal"crimetals,

willl facilitate,` when the-cell Vis' subsequently rel.l charged, the: charging of-` thef main-V -metal dor; metals at thecostsof said: auxiliary,k metal; that is to say without loss of efficiencyroftheicell: VOf:` course.. che cur-ves l. abovef'referred to are gicenL-merelyeby-'way oexample.

t Egs. ffandi showaa. storage-bell made according-to :my invention;

The :fluidtighti sealedfvesselisrshowrr at lf. rIn, side; this vessel and in; the central) part* ist' the positive;l electrode 5; madeofnickelfoxid and; graphitegplacediin aperforated'v` cylinderaofrnicker electrodev is infeontact'A witlxj' the'. positive .terminali 2i .The.negativefelectrodefis lor-:atediin-.the:space` adjoining. thefninnerwallfoff vessel: Iii 'Itis-#conev stituted by-ipowderyicadmiumand the potential'V of-.this electrode*will*Y riseso thatthe curveff'" f Y l ironelated :mfperfcrated-"bagsflottima-and' Steel?" as' visible: on

Fig. 6. A small plate 'Lof a conductor material connects this negative electrode 4 with Vthe negative terminal 3. i i In the annular space between electrodes 4 and 5 there is a nylon strip 6 limpregnated with the electrolyte and wound three or four times about electrode 5. i

4As above stated, according to my invention, if the metals constituting the electrod es are, for instance, nickel for the ;pcsitive electrode and cadmium for the negative electrode, the amounts of these metals, i. e.-their capacities, and their statesof oxidation must comply with the following conditions when vessel I is sealed: v i

I. The ratio of the,lcapacity"of"the positive electrode to the capacity. of the negative electrode is:` t 1\a|b.

1I. If the positive electrode .is fully charged, i. e. wholly in the form of oxide, a proportion of the negative electrode is in the metallic state and a proportion in the state of oxide, a representing the amount of metal of the negative electrode which is to give the excess of charge thereof over the positive electrode and b the amount of this metal which remains always uncharged, i. e. in the state of oxide.

The iirst condition is easy to comply with by suitably choosing the amounts of metal used for the two electrodes respectively. The second one can be complied with by, on the one hand, fully charging the positive electrode and, on the other hand fully charging the negative electrode and then discharging it in the proportion As above stated, a and b are advantageously chosen equal both to 0.25.

In a general manner, While I have, in the above description, disclosed what I deem to be practical and eiicient embodiments of my invention, it should be well understood that I do not wish to be limited thereto as there might be changes made in the arrangement, disposition and form of the parts without departing from the principle of the present invention as comprehended within the scope of the accompanying claims.

What I claim is:

1. In the method of making a gastight storage battery cell the steps of placing in a container an electrolyte, a positive electrode and a negative electrode having a higher capacity than the positive electrode, the condition of said negative electrode corresponding, prior to sealing, to a higher charged state than the condition of the positive electrode, the diierence between the charged states of said two electrodes being at most equal to the difference between their ca pacities, and hermetically closing the container.

2. A gastight storage cell which comprises a sealed vessel, a positive electrode in said vessel, a negative electrode in said vessel in a state of charge higher than that of said positive electrode and having a higher capacity than said positive electrode, and an electrolytein contact with both of said electrodes.

is at least equal to the overvoltage of said mainv metal, the amount of the main metal. of the negative electrode being so adjusted that its com-` plete discharge takes place at about the 4same time as the complete `discharge of the main ac-V tive mass of the positive electrode, whereby kthe further discharge ci the negative electrode is' dueto the oxidation of the auxiliary metal and l the further discharge of the positive electrode is due to the oxygen taken up by said auxiliary ingredient.

4. A gastightstcrage ceu according@ e1a1ia3`-` in which said auxiliary metal is copper.

5. A gastight storage cell according to claim 2 in which the difference of charge between between the electrodes is smaller than the difference between their capacities.

6. A gastight storage cell of the character described comprising a sealed vessel capable of confining under pressure the gases generated therein, and in said vessel a positive electrode and a negative electrode, said negative electrode having a higher capacity than said positive electrode and the oxidation states of said two electrodes being so adjusted that the capacity of the negative electrode to accumulate electric energy under the influence of a charging current is higher than that of the positive electr-ode.

7. A gastight storage cell of the character described comprising a sealed vessel capable of confining under pressure the gases generated therein, and in said vessel a positive electrode, and a negative electrode, the ratio of the capacity of the positive electrode to the capacity of the negative electrode on sealing the vessel being thereby ensuring that when the positive electrode is fully charged a proportion of of the negative electrode is in the metallic state and a proportion in the state of oxide, a representing an amount of metal in the negative electrode giving an excess of charge over the positive electrode and b representing an amount of metal remaining always uncharged. i. e. in the state of oxide, a and b being each approximately .25.

8. A gastight storage cell as dened in claim 2 wherein the auxiliary ingredient of the active mass of the positive electrode is graphite.

9. A gastight storage battery cell which comprises a sealed vessel capable of confining under pressure the gases generated therein, and in said vessel an alkaline electrolyte, a positive electrode containing in the active mass nickel oxide which is oxidized to a higher oxidation degree on charging, and a negative electrode con- :ma-63ans taining theroxide/ o1'`v a; --met'ar selected'from the.

`groupeonsisting ofl lronand cad'mumggwhbh oxide isreduced co the'metal on charging', said negative electrode' having a; lhigher capacity' than the; positive electrode andVV the amount of metafon. the-negative electrode'exceedng et any time substantially the -e-lectricaly equivalent proportion of higheroxdzed nickel oxide smu1taneousl'yf'presenty in"v 'the activel lInassyof' *the pasitive in a container an alkaline; electrolyte-,Ja posiwe electrode echtem-ing in the active-mass. nekelf oxice',. which is' oxidized: yto a. higher-"oxidation degree un' cher'reingr and a negative eleetrode. con taining: theoxde of'- a; metal selected: from- .the group-'consisting of* iron: and cadmium whithoxidel sffreduceelI to the metal on charging` saidnegatifvel-eleatrode hav-ing higher lcapacityv than he-avpestvef-Helectrode; providing, mier" tothe sealing, of the container, a plropofsorrf'metalK on: the: negative 'electrode' exceeding substantially the eIectn'eaIl-yf-equivalent. repel-tim et hfeher oxidized-m'ckei 'oxdehsimultaneeusly Ypresex'xtzf.1m' the active mass of the positivey electrdde; thereby obtaining' the' `negative l eectrod f an higher charged* stetter4 than the positive .eectzfodeywhedereneebetweem .the charges. bengamadeat most equal to the difference between'the'capac ties;-a-ndhermeicauy closing the" container-while the negative eleetrode ist thus-higher charged than the'y ,pU'sitive-f electrode.

Numbe Name Date 721,682 Edison Mar."3',"903

2,213,128 Langguth..-... Aug. 27, 1940 Numb@ lCountry "Date 317,130 Great Britain Aug. 12, 1929 

1. IN THE METHOD OF MAKING A GASTIGHT STORAGE BATTERY CELL THE STEPS OF PLACING IN A CONTAINER AN ELECTROYLTE, A POSITIVE ELECTRODE AND A NEGATIVE ELECTRODE HAVING A HIGHER CAPACITY THAN THE POSITIVE ELECTRODE, THE CONDITION OF SAID NEGATIVE ELECTRODE CORRESPONDING, PRIOR TO SEALING, TO A HIGHER CHARGED STATE THAN THE CONDITION OF THE POSITIVE ELECTROD, THE DIFFERENCE BETWEEN THE CHARGED STATES OF SAID TWO ELECTRODES BETWEEN THE MOST EQUAL TO THE DIFFERENCE BETWEEN THEIR CAPACITIES, AND HERMETICALLY CLOSING THE CONTAINER. 